The invention relates to a linear-drive cylinder having a cylinder tube in which a piston is mounted displaceably in the longitudinal direction, with a force-transmission means which forms a driven member and which is connected to the piston and is guided out of the cylinder tube.
Linear drives known in practice are so-called linear modules, in which a piston is moved via a pressure medium or via pull means in an elongate, essentially closed or laterally slotted guide tube, said piston actuating machine elements to be driven, by means of suitable force-transmission means, such as, for example, a piston rod or a driver passing through the lateral slot of the guide tube. In all these linear drives, the guide tube of greater or lesser length is closed on the end face by means of a cover or closing piece. When the linear drive is actuated by pressure medium, this cover serves for sealing off the chamber otherwise limited by the piston and the guide tube. When the linear drive is actuated by a pull means, a gear and a motor, such as, for example, a stepping motor, are arranged on the closing piece. To fasten the respective covers on the guide tube, it is usually necessary to carry out relatively complicated machining operations on the guide cylinder which is otherwise simply cut to length from prepared semi-finished products.
A linear drive actuated by pressure medium is known from GB 1,329,629. This has a longitudinally slotted guide tube which is sealed off via a flexible band and in which is mounted in a sealed-off and displaceable manner a piston which passes with a flat driver through the lateral slot of the guide tube. The guide tube is closed on the end faces by means of covers resembling cylinder heads. For this purpose, the guide tube is provided with an external thread. The respective covers have corresponding internal threads which engage with the external thread of the guide tube.
In this linear drive, after the guide tube has been cut to length it is necessary to apply an external thread to the ends of the guide tube.
A pressure-medium cylinder having a likewise longitudinally slotted cylinder closed on the end faces is known from EP 0,113,790 A1. This has a cylinder tube, in which is mounted in a longitudinally displaceable and sealed-off manner a piston which passes through the lateral slot with a web-like part which, in conjunction with a force-transmission element, serves as a driven member. The cylinder is closed on the end face by means of a cover which has a cylindrical portion projecting somewhat into the interior of the cylinder tube. Adjacently to the cylindrical portion, the diameter of the cover increases, so that the latter has an annular shoulder. The annular shoulder bears on the end face of the cylinder tube. To fix the cover to the pressure-medium cylinder, threaded bores, into which fastening screws passing through the cover are screwed, are made in the end face of the cylinder tube.
During the production of the cylinder tube, it is necessary, after a correspondingly prepared semi-finished product has been cut to length, to make a plurality of threaded bores in the cylinder tube in a manner distributed over the end face. This presupposes a minimum wall thickness which cannot fall below a set value.